Hierarchical NiCoO2 single-crystalline nanoflake arrays on Ni foam for supercapacitors and Li-ion batteries application

Highlights: • Single-crystal NiCoO₂ nanoarrays are synthesized by hydrothermal method. • The specific capacitance is high up to 1448 F g⁻¹ for supercapacitors. • For Li-ion batteries, it shows ultrahigh charge specific capacity of 1130 mAh g⁻¹. • It provides an accessible approach to improve electrochemical performance of NiCoO₂. In this work, hierarchical single-crystal NiCoO₂ self-supported nanoflakes arrays grown on Ni foam were successfully prepared through a facile hydrothermal process. The nanoflakes can well contact with the substrate and support each other to form an open stable structure. This design of architectures can relieve volume expansion of metal oxides, promote the fast diffusion of electrolyte and increase electroactive sites. When applied in supercapacitors, the as-prepared NiCoO₂ shows ultrahigh specific capacitance of 1448 and 962 F g⁻¹ at 3 and 20 A g⁻¹ for supercapacitors, respectively, indicating good rate capability. Moreover, NiCoO₂ nanoflakes arrays exhibit excellent lithium storage capacity for lithium-ion batteries application. The charge specific capacity is high up to 1130 mAh g⁻¹. This work provides an accessible approach for improving electrochemical performance of NiCoO₂.